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Diseases of Aquatic Organisms

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DAO 58:143-150 (2004)  -  doi:10.3354/dao058143

Phylogenetic study and identification of Vibrio splendidus-related strains based on gyrB gene sequences

Frédérique Le Roux1,*, Mélanie Gay1, Christophe Lambert2, Jean Louis Nicolas3, Manolo Gouy4, Franck Berthe1

1Laboratoire de Génétique et Pathologie, Institut français de recherche pour l¹exploitation de la mer (IFREMER), 17390 La Tremblade, France
2Laboratoire des Sciences de l¹Environnement Marin (LEMAR), Université de Bretagne Occidentale (UBO), Place Copernic, technopole Brest-Iroise, 29280 Plouzané, France
3Laboratoire de Physiologie des Invertébrés Marins, IFREMER, 29280 Plouzané, France
4Laboratoire de Biométrie et Biologie Evolutive, Unité Mixte de Recherche 5558, Centre National de Recherche Scientifique (CNRS), Université Claude Bernard, Lyon, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France

ABSTRACT: Different strains related to Vibrio splendidus have been associated with infection of aquatic animals. An epidemiological study of V. splendidus strains associated with Crassostrea gigas mortalities demonstrated genetic diversity within this group and suggested its polyphyletic nature. Recently 4 species, V. lentus, V. chagasii, V. pomeroyi and V. kanaloae, phenotypically related to V. splendidus, have been described, although biochemical methods do not clearly discriminate species within this group. Here, we propose a polyphasic approach to investigate their taxonomic relationships. Phylogenetic analysis of V. splendidus-related strains was carried out using the nucleotide sequences of 16S ribosomal DNA (16S rDNA) and gyrase B subunit (gyrB) genes. Species delineation based on 16S rDNA-sequencing is limited because of divergence between cistrons, roughly equivalent to divergence between strains. Despite a high level of sequence similarity, strains were separated into 2 clades. In the phylogenetic tree constructed on the basis of gyrB gene sequences, strains were separated into 5 independent clusters containing V. splendidus, V. lentus, V. chagasii-type strains and a putative new genomic species. This phylogenetic grouping was almost congruent with that based on DNA-DNA hybridisation analysis. V. pomeroyi, V. kanaloae and V. tasmaniensis-type strains clustered together in a fifth clade. The gyrB gene-sequencing approach is discussed as an alternative for investigating the taxonomy of Vibrio species.

KEY WORDS: Phylogenetic · GyrB · Vibrio splendidus · Polyphyletic · Taxonomy

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